It is known that hydrolysable sulfur-containing organosilicon compounds are capable of reacting with fillers containing hydroxyl groups, such as natural and synthetic silicates, carbonates, glasses and metal oxides. In this context, they are used for surface modification and promotion of adhesion. In the rubber processing industry, they are employed as adhesion promoters between the reinforcing filler and the polymer employed (Angew. Chem. 98, (1986) 237-253, DE2141159, DE2212239, DE19544469A1, U.S. Pat. No. 3,978,103, U.S. Pat. No. 4,048,206, EP784072A1). The best-known representatives of this substance class include the polysulfane(alkyltrialkoxysilanes), such as, for example, bis[3-triethoxysilylpropyl]tetrasulfane or bis[3-triethoxysilylpropyl]disulfane.
The use of mercapto-functionalized organosilanes in rubber mixture is also known (U.S. Pat. No. 3,350,345, FR2.094.859). The use of alkylsilanes for lowering the viscosity of rubber mixtures (EP795577A1, EP864605A2) and the combination of mercapto-functional silanes with longer-chain alkylsilanes (DE10015309A1) are likewise known.
A disadvantage of the use of the trialkoxy-functional silanes is the emission of volatile hydrocarbons, these chiefly being methanol and ethanol in practice. Dialkylmonoalkoxysilyl polysulfides are known from DE1043357A1 and EP1244676B1. Due to the dialkylmonoalkoxy group, the emission of volatile hydrocarbons is lower than in the case of trialkoxy compounds. Disadvantages of the dialkylmonoalkoxysilyl polysulfides are the poor abrasion and tear propagation resistance.
The object of the present invention is to provide rubber mixtures during the preparation of which a low emission of volatile hydrocarbons occurs, and the rubber mixtures have an improved tear propagation resistance compared with rubber mixtures with known silanes.